The field of the invention is in the art of accelerometers and more particularly that of inertia switching devices.
It is frequently desirable to "turn on" ("enable" and "activate" also are synonymous, frequently uses terms) and electrical circuit when a relatively sudden and abrupt change of velocity occurs, i.e., an acceleration greater than a predetermined amount. The term "acceleration" is presumed to include both the positive and negative. Thus, de-acceleration is negative acceleration with the velocity vector still in the same direction. Inertia is that tendency of a body to resist acceleration. The inertia-activated electric power source of this invention provides a voltage on a pair of external terminals on the happening of a predetermined magnitude of acceleration. Generally, inertia-activated devices are well known. The use of an inertia device to activate restraining air bags that inflate on the collision of an automobile is a typical well-known example. The term "set back-actuated" is frequently applied to devices sensing forward thrust or positive acceleration, while "impact-actuated" is frequently applied to similar devices sensing sudden slowing or stopping, i.e., de-acceleration or negative acceleration. Typical examples of the former are devices for sensing the launching of airplanes, missiles, and projectiles, while typical examples of the latter are collision-sensing devices, excessive package handling load sensing devices, and safety beacon actuated devices.
Generally, inertia devices are rated as to the number of G's required to activate them, G being the acceleration of gravity under standard conditions on the surface of the earth. Generally, inertia devices may be used for either positive G forces or negative G forces by merely turning them around. In some instances, it may be desirable to take into consideration a slight change in calibration due to a change in static load.
An inertia-activated device must generally be very rugged and reliable. Quite frequently, they must withstand and continue to function after experiencing shock forces many times greater than that at which they initially operate. Many prior art devices are quite complex and their reliability to withstand shocks of greater magnitude than they were designed to sense is relatively low. Generally, prior art inertia-activated power sources are merely inertia switches connected by wiring to a battery with each requiring shock protection. It is thus an object of the present invention to provide an inertia-activated electrical power source in which a battery, in addition to supplying the electrical power is also the actuating element in sensing the acceleration.
It is another object of the invention to provide an extremely rugged, relable inertia-activated power source that may readily be adjusted for various G load activating forces.
It is another object of the invention to provide an inertia-activated electrical power source that upon activation latches in the "on" position.
It is another object of the invention to provide a positive action device that is either "off" or "on" without any chattering, or partial or intermittent contacting of the internal electrical circuits of the device.
It is another object of the invention to provide an inertia device in which the moving element may readily be cushioned to arrest its motion toward the end of its travel thus preventing any undue shock damage.
It is yet another object of the invention to provide an inertia-activated electrical power source that has extremely few parts, is simple and economical to manufacture.